CROSSLINKING OF POLYCAPROLACTONE IN THE PRE-GELATION REGION

Polycaprolactone (PCL) crosslinked below the gel point either with peroxide or by exposure to ionizing radiation was compared by rheological studies. As a result of peroxide crosslinking, PCL increases in viscosity and shear rate dependence and exhibits increased dynamic moduli that converge at higher frequencies. The analysis of gases evolved from $gamm-irradiated PCL shows that the yield of hydrogen (G=0.39) approximates the sum of the yields of carbon monoxide (G=0.19) and carbon dioxide (G=0.21). It is inferred that equal amounts of crosslinking and scission result from ionizing irradiation. As a result, PCL is converted by irradiation to a densely branched system. Steady shear viscosities do not depend strongly on dose and overlap at higher shear rates. Similarly, dynamic moduli, especially G″, become less sensitive to dose.